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Home to roost

Pukorokoro Miranda Naturalists’ Trust bought a piece of land in the Firth of Thames to ensure it will always be a safe roost for shorebirds.


Image - Keith Woodley, Pukorokoro Miranda Naturalists' TrustOne of the great stories we tell here is the story of the bar-tailed godwit, a wonderful flagship for the shorebird clan, if you like. The godwits here have all nested in Alaska, they’ve all hatched in Alaska, they are all birds from the tundra, and they migrate to New Zealand after breeding every year. That migration involves a single flight across the Pacific, without stopping. In early September, when they arrive, their wings are drooping, they’re really skinny, and in extreme cases you will find a bird that’s having difficulty standing up because it’s touching down for the first time having flown 12,000 kilometres to get here.

Another cool thing about these birds is the way that they link us. They link us with habitats in East Asia around the Yellow Sea where they stop to refuel during their northern migration, and they link us with the coastal mudflats of Alaska and the tundra where they breed. All these birds require habitats in three different parts of the planet, and all of those parts are equally important. If one of those parts was to disappear, the whole migration system would fall down.

What they need when they get here is a lot of food to recover from the flight. They need enough food to double their weight before they leave in March. So the Firth of Thames and other parts of the country are incredibly important for these guys. They need a lot of food to sustain this lifestyle.


Images - seabirdsMost shorebirds find their food on the mudflats when the tide is low. Here, there’s something like 8000 hectares exposed at low tide. When the tide is up they can’t access that food and they get pushed off the tidal flats and form big flocks, they roost. When you think about it, they are pushed off the mudflats and up against us and all of our activities, our development, and all the things we do along our coastal margins, and so they are very prone to disturbance.

Another issue has been the expansion of mangroves. The clearing of forest, drainage of the Hauraki Plains, urban and farmland development – from that you get a lot of sediment, you get a lot of nutrients coming off the land. In essence we have created perfect conditions for mangroves. The mangroves have taken out some shorebird roost sites because if you are a shorebird roosting on a high tide you want to be able to see around you 360 degrees to feel safe from predators and danger. I also suspect the increase of the mangrove zone has reduced the net area of tidal flats available for foraging.

Maintaining a protected secure roost site for these guys is as equally important as securing the health of the mudflats where all the food is. The roosting time is important for shorebirds because they use it for daily maintenance. They preen, they sleep; they probably catch up with the local gossip because there is always a lot of chatter on a roost site. Around the Firth of Thames, there are a number of places shorebirds can roost on the lower high tides but when you get the higher tides they all come over here, to our Stilt Ponds.


Image - Keith Woodley


This land, which the trust purchased in the last couple of years with assistance of Waikato Regional Council and Foundation North, is incredibly important for the ponds alone. But it’s also important because it has a major roosting and foraging area on the lower high tides, a big area of mudflats on the inside of the shell spit. We seek to keep that area open and available for shorebirds. Every year around September we have a working bee. We have a lot of fun going out there in the deep mud and pulling out mangrove seedlings. We have got a resource consent to do this, so we are doing this under an official umbrella.

This land has been covenanted by QEII trust for the last 20-30 years, but buying it means we can now manage it. We are working on a management plan and that’s going to involve a number of things. Weed control is going to be a major one, but we want to better manage the levels of the Stilt Ponds. It’s not draining as well as it should so we want to dig a new channel across to the tidal channel, and put a sluice gate in. Waders – shorebirds – require shallow water. If the water is too deep they won’t use it. Silt has been clogging the ponds and they’ve been backing up in the high tides, and we’ve had a lot of rain – so we have had an influx in black swans. Now, we call these the Stilt Ponds, we don’t want them to be Swan Lake. The idea is to maintain it as optimal habitat for shorebirds which means lowering the water levels and politely evicting the swans.